In an emergency, this DIN-to-CGA870 adapter allows the DIN fitting on diving gas blending transfill kits used for filling SCUBA cylinders to also be used to transfill USP oxygen to the pin-indexed CGA870 fitting found on some emergency oxygen cylinders. In an emergency when a CGA870 oxygen regulator and mask is not available, it could also be used with a suitable SCUBA oxygen regulator to provide demand oxygen from a medical oxygen supply cylinder with a CGA870 valve.

Usage note: Most bulk oxygen sold in returnable cylinders has the US standard CGA540 valve, so typical DIN-to-DIN transfill hoses with this adapter would only allow transfill from medical oxygen cylinders with the CGA870 valve to SCUBA cylinders. Our Deluxe Blending & Transfill Kit and our Deluxe Fitting & Hose Kit for our gas booster both include a CGA540 fitting and terminate in a standard DIN fitting, meaning this adapter would allow transfill from bulk oxygen cylinders to emergency oxygen cylinders with a CGA870 valve.

According to our suppliers, their Nitrox Ready and Oxygen Service products are compatible with oxygen and factory cleaned for use with compressed gases in excess of 23.5% oxygen. Nonetheless, the 'clean state' of this equipment applies only prior to initial use. Thereafter, periodic inspection and cleaning are a necessity. You must meticulously follow the recommendations of the US Department of Transportation (DOT), Compressed Gas Association (CGA), and other federal/state/local agencies, plus your dive training agency for equipment maintenance, handling, storage, labeling, filling, transport and use of compressed gases. Oxygen-related fires and explosions can result in serious injury or death. Ultimately, you must make the final decision to assume all risks associated with the use of any compressed gases, including those in excess of 23.5% oxygen.

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How do the grades of compressed oxygen differ?

There are three grades of compressed oxygen gas widely sold in returnable supply cylinders: Aviation (aka ABO), Medical, and Industrial (aka Welding). The gas itself is normally produced using cryogenic separation of air, resulting in a gas that is very close to pure oxygen: > 99.5% with the balance being inert gases, mostly argon. Nearly all oxygen sold in the US is what is known as USP quality, meeting or exceeding United States Pharmacopeia quality standards for human consumption. As a practical matter, the differences in the three grades as sold today are not quality of the oxygen being put in the cylinder but rather the procedure used to fill the cylinder and, in the case of Medical grade, licensing or documentation requirements.

Industrial grade oxygen cylinders can be just topped up when refilling and, although unlikely, could be contaminated with other unknown gases that might have back-flowed into the cylinder during use or filling. Aviation and Medical grades must have the cylinder completely evacuated before every fill and each batch is tested for purity. Medical grade oxygen is legally regulated in the US by the Food and Drug Administration and filling a cylinder for medical use incurs some FDA licensing and documentation requirements for the cylinder fill station operator. Medical oxygen is considered a drug, and thus requires a doctors prescription for the FDA licensed fill station operator to fill the cylinder. The FDA has granted an exception to the prescription requirement for medical cylinders marked as emergency use only, but they still should only be filled with USP quality oxygen and following FDA guidelines. To blend breathing gas mixtures for Nitrox and technical diving, most blenders use Aviation grade oxygen to avoid the FDA licensing and documentation requirements yet still use an oxygen grade suitable for human consumption.

Among divers, perhaps the most often debated topic about oxygen grades is should industrial grade oxygen be used for SCUBA applications. That's because welding oxygen is relatively cheap and brand name compressed gas suppliers usually fill oxygen cylinders from the same high quality source while following best practices regardless of grade. However, small welding supply operations are more likely to just top up their industrial grade oxygen cylinders from a local bulk supply and may not follow best practices. Unless the entire supply chain for each and every cylinder of oxygen can be trusted with absolute certainty, in our opinion using industrial grade oxygen for diving applications is a needless risk.

For much more detail about types of oxygen, especially recommendations regarding applications found in diving and diving emergencies, read Oxygen: Concentrations, Grades, and Labels by Larry "Harris" Taylor, Ph.D.